BackgroundSurgical site infection (SSI) is an infection that occurs after surgery within 30 days in the part of the body where the surgery took place. Some of the common symptoms are: drainage of cloudy fluid from the surgical wound, pain or tenderness, localized swelling, redness, and raised body temperature. Lack of data on surgical site infection among women who underwent cesarean section (C/S) initiated us to undertake this paper which is targeted to assess the magnitude and determinants of SSI among women who underwent cesarean section.MethodsRetrospective document review study design was conducted among mothers who underwent cesarean section in Ayder Comprehensive, Specialized Hospital (ACSH) from September 2014 –January 2016. Mother’s charts were selected using systematic random sampling technique. Data were cleaned using EPI info version 3.5.1 and analyzed using SPSS version 20. Descriptive statistics, Bivariate, and multivariable logistic regression were conducted to summarize the data.ResultA total of 206 medical records of women who underwent C/S in ACSH comprehensive specialized hospital were reviewed. The mean age was 27 years (+ 5 year). The magnitude of surgical site infection was 11.7%. Premature rupture of membrane (PROM), prolonged labor, rural setting, human immune deficiency Virus, chorioaminities and blood loss showed significant association [(AOR = 8.818 95%CI (21.71–35.816)], [AOR = 16.17, 95%CI (2.850–91.819), [AOR = 5.666,95%CI (1.568–20.483)], [AOR = 6.982,95%CI (1.382–35.269), [AOR = 16.17,95%CI (2.850–91.819)] and [AOR = 0.097,9%CI (0.017–0.569)] respectively.ConclusionThe magnitude of post C/S infection in this study 11.7%. PROM, prolonged labor, residence, HIV, Chorioaminities and blood loss are considered to be an independent risk factor.